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Hey everyone,

Got a question. So my block heater isn't working as far as I can tell. I pulled the starter off the truck today because I think that went kaput and I needed to have it tested. Once out of the way, I found the block heater (had never tried to locate it before). I felt around the area where it's plugged in (I'm talking the bottom of the engine) to see if it was warm at all. It was cold as ice (well... cold as the 45 degree weather we're having). It's been plugged into the garage for about three days now. Anyways... I pulled the plug out of the block heater. The three prongs (male end?) were all covered in a greenish corrosion, much like what you'd find on dirty battery terminals. So here are my questions:

1) How do I determine what works and what doesn't with this system (what are the troubleshooting procedures)?

2) If I want to replace the block heater (and I think I do if it's broke), where do I find one and what would I expect to pay for it?

3) What is the procedure for replacing the block heater?

4) Finally, I watched a youtube video on this subject that was, in large part, very unhelpful. It was mostly a guy complaining about how cold it is in Alaska. He did, however, mention that rather than replace the inoperable block heater, that there was an aftermarket heater that could be installed somewhere in the coolant system. Does anyone know what that's about and if that's a viable option?


I appreciate any and all help you all can throw my way. It's getting colder every day, and Mable doesn't like the cold one bit. :)

Cheers!
 

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I can't help you much on the block heater on the 6.9 on weather it is a freeze plug type or a screw in type but 99.99% of all problems with the block heaters is with the cord or plug on the end of it. They flop around so much that they break the conductors inside the cord. You can usually just get a short heavy duty extension cord and cut off the female end and then attach that cord to the block heaters cord.

But before I did that I would get a volt/ohm meter and check the resistance of the heater just to make sure.
 

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I remember years ago that Napa stocked the same block heater and the cord (which they sold separately). Evidently they were available from the same vender who furnished them to Navistar.
 

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You check it like you would any other heating element; check the resistance. If it is anywhere from around 14 to 40 ohms it is probably fine. Check it without the cord to eliminate the cord as the problem. You should scrape the tarnish off to make sure you have a good connection.

Keep in mind, they make them at different watts. The higher the wattage the hotter they get.

Drain your coolant, replace the plug, refill the coolant with some good heavy duty sca coolant.
The plug should have a little screw in the center, unscrew it a bit and it should pull out.
 

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Like any other electrical terminal, those prongs need to be cleaned to make a good connection (even with a test meter). Steel wool is good for male terminals; females can be more difficult (universally! ;)). Once they're clean, apply electrical grease (not conductive, or thermal, or dielectric, or chassis) to keep them that way longer.

1) Measure resistance from each heater terminal to each other terminal, and to the block (ground). Between the hot & neutral terminals, resistance should be ~5~10 Ohms (depending on the heater's designed output). Between either of them & ground should be >10K Ohms. With the cord UNplugged at BOTH ends, resistance from any terminal to any other on a different wire should be >10K; to the terminal at the other end of the same wire should be <5 Ohms.

2) Amazon, eBay, parts stores, dealerships, Jegs, Summit, JCWhitney, FordPartsGiant... Pay as much as you have to, but as little as you can.

3) Click this & read the caption:



4) You tell us - what brand/model/name did he use for it? Was it a circulating heater that installed inline in the lower radiator hose? Yes, they're more effective, but more expensive to buy & operate.
 

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If it's over by the starter, it's ^^^^^ a freeze plug type. (Later trucks have an insert into the oil cooler.) Should be 1000 watts. Plug in Ohm's law, carry the 2, 30 days has September.... and it should be aprx. 14 ohms. If resistance at the heater itself is correct, clean the terminals as said, reconnect the cord and measure resistance at the hot and neutral terminals of the far end of the cord. If that resistance is close, then you should be GTG. If not, try cleaning the terminals on both ends of the cord, and if that still fails, replace the cord (as said, available separately online and from NAPA).
 
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